1. Field of the Invention
This invention relates to signs illuminated by edge lighting. This invention also relates to the use of discrete light sources, such as light emitting diodes to illuminate a figure, so that only the figure is illuminated relative to the substrate on which the figure is formed.
2. Description of the Prior Art
Edge lit signs or signboards employing fluorescent lamps mounted adjacent one edge of a light transmissive panel have been employed to illuminate characters or figures on one face of the panel. Since a standard tubular fluorescent lamp emits a substantially uniform illumination along its entire length, it will uniformly illuminate a figure or a series of characters extending between opposite ends of the fluorescent lamp and presumably along substantially the entire length of the sign.
It has been recognized that light emitting diodes possess certain advantages over fluorescent lamps when used in edge lit illuminated signs. U.S. Pat. No. 6,341,440 is one example of the use of a series light emitting diodes or LED's disposed in a linear array in such a sign. Of course, standard LED's comprise discrete light sources when compared to a standard tubular fluorescent lamp. In order to illuminate a series of characters on a clear panel, it is therefore necessary to disperse or diffuse the light emitted by discrete LED's. U.S. Pat. No. 6,341,440 employs a light diffusion strip with a series of semicircular holes in which individual LED's are located. This diffusion strip is separate from the clear panel containing display characters or ornamental markings, and the diffusion strip is located adjacent one edge of the clear panel. According to this patent, the light is diffused so that the light emitted by individual LED's can enter an edge of the panel with a uniform hue, which presumably means that the light from individual LED's is diffused before entering the clear panel.
U.S. Pat. No. 6,615,520 discloses another example of an edge lit sign employing discrete LED's. In this version, LED's, fiber optic devices or halogen bulbs are fitted in tight fitting orifices along one edge of the panel. These orifices are described as tight fitting and well polished to allow for optimum transmission of light from the discrete light sources into the display board. Improved light transmission and efficiency is apparently of paramount importance. To diffuse the light, this device apparently employs reflective strips located in a receptacle in which the display board is mounted. The edges of the display board slope away from the centrally mounted LED's so that reflective walls of the panel insure little loss of light.
U.S. Pat. No. 6,481,130 is another example of an edge lit sign that employs a separate member to disperse the light form discrete LED's. This device employs both a reflector and a lens portion.
These devices, however, use a separate diffuser and light transmissive panel and appear to require precision in mounting the LED's relative to either the diffuser or the clear panel. These devices also appear to use a rather small number of LED's. For example, U.S. Pat. No. 6,341,440 shows three sets of red, blue and green LED's and U.S. Pat. No. 6,615,520 shows only three LED's. It would appear to follow that these devices must either employ relatively strong LED's or the displayed light intensity must be relatively weak. These devices also employ multiple components that appear to require precision in assembly.
The instant invention employs a light transmissive panel that includes both geometric figures or display characters and a diffusion surfaces that are integral part of the one-piece panel. This simplifies construction and provides an economical means for employing a relatively larger plurality of discrete light sources, such as LED's.